Introduction to location based services:
Location based services are rapidly expanding. Outdoor location technologies are mainly based on GPS technologies. GPS cannot perform properly indoors, and is therefore inadequate. As a result, indoor location systems are appearing on the market.
The need for a system, such as the indoor navigation system disclosed herein, arises from various market segments and applications. One example in the market is the GPS based systems that use integrated positioning and navigation systems based on GPS receivers as the primary positioning technology. Subsequent to the events of September 11th, the Federal government mandated that GPS capability be built in to all cellular phones. However, the fact that uninterrupted satellite reception is not possible in many locations is a major limitation of GPS based systems. Densely populated areas and radio-frequency-signal shadowed locations, such as urban centers (a.k.a. “urban canyons”), generally do not allow proper operation of GPS, yet it is in these locations that the need is greatest.
There is a clear need for a cost effective system that maintains performance indoors, in urban canyons and in city centers.
Another important consideration is that GPS itself is susceptible to jamming and other man-made interference.
Description of GPS System.
The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. GPS serves marine, airborne and terrestrial users, military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) that provides civilian users with 100 meter accuracy as to the location or position of the user. For military users GPS provides the Precise Positioning Service that is accurate to within 20 meters. Both of these services are available worldwide with no requirement for any local equipment.
View of GPS limitations:
First limitation of GPS is that upon activation the GPS receiver scans for signals from the GPS satellites. A unit must locate and receive signals from at least four satellites to be able to determine its location. This process of locating the satellites, receiving the data and achieving a position fix can take several minutes. This delay is problematic for many GPS applications.
Second limitation of GPS is that the receiver needs a clear view of the sky to successfully receive signals from the satellites, again under unfriendly RF conditions such as inside buildings, or in “urban canyons” or in the shadows of high buildings, the GPS suffers from multi-path effects and therefore shows poor performance, or none at all.
Third Limitation—limited accuracy: There is a problem of limited accuracy of the civilian GPS signal. While knowing your position to within 50 to 200 feet anywhere on the planet is a major technological feat, it is still not accurate enough, to locate and navigate to an a store in a mall or to empty parking space, where each space measures about 10 feet, and most indoor store/malls are located where the GPS cannot work effectively.
Existing navigation systems, such as the new mandatory GPS equipped cellular phones, are based on GPS and have the aforementioned limitations.
Another significant factor adding to the limitations of the GPS based systems is the important role of map production; normally a user, requires a map to be as detailed and as up-to-date as possible. The existing maps used by the GPS based systems provide limited detail and are not able to reflect changes on a real time basis, more over there is no mapping for indoor facilities at all. The recent introduction of imagery services, such as Google Earth and its competitors, that are offered as an enhancement to GPS at a fee, still provide out of date information, with the unsatisfactory result that users encounter road changes and area development not shown on the maps and imagery.
Application:
In general, the disclosed system is based on applying machine-learning techniques to the task of inferring aspects of the user's status from a stream of input from sensors.
The system focuses on indoor navigation, or navigation in crowded urban areas, where GPS based systems, due to lack of access to satellites or the GPS limitations detailed previously, cannot achieve the required results.
The system have focuses on the task of interactively guiding the user to a desired indoor destination.
Examples of indoor applications:
The user may wish to locate an empty available parking space in his vicinity.
The user may wish to locate a specific store in a shopping mall, or a particular aisle in a department store, or a specific item on a shelf.
The user may wish to locate a specific conference room in a convention center, or a point of interest in an amusement park or a point of interest in a museum.
The user may be looking for a train location in a station, or stops in a subway or underground train system.